Concentration of timolol in aqueous humour

Two groups of twenty patients who were to undergo a routine e.c.c.e. applied eye-drops containing timolol 0.1% or 0.5% twice daily during the week preceding their operation. A third group of twenty patients, using placebo drops, served as control. During the cataract surgery a sample of aqueous was collected. The samples from the timolol 0.1% patient group contained a significantly lower concentration of timolol than those from the timolol 0.5% patient group, but there was considerable overlap.